Cannabis administration is associated with reduced alcohol consumption: Evidence from a novel laboratory co-administration paradigm.

Background: Alcohol and cannabis co-use is increasingly prevalent across the U.S., concomitant with trends towards recreational cannabis legalization. While some studies have shown that cannabis co-use is associated with reductions in alcohol consumption (i.e., substitution), others have observed increases in alcohol intake (i.e., complementarity) or no change. This study aims to address this gap in the literature through investigating the effects of legal-market cannabis on alcohol consumption and craving in the laboratory.

Method: Leveraging a within-subjects design, we enrolled non-treatment seeking individuals who use both alcohol and cannabis (n = 61) to complete two laboratory sessions, wherein they were provided an alcohol priming drink alone or after self-administering cannabis. Participants were then given the opportunity to self-administer up to 4 additional drinks. We assessed differences in alcohol self-administration and craving between sessions.

Results: Cannabis self-administration was associated with a significant reduction in number of drinks self-administered. Further, exploratory analyses revealed that individuals who drank less after using cannabis ("substituters", n = 23) experienced reductions in craving after using cannabis and alcohol compared to alcohol alone, whereas individuals who drank the same number of drinks after using cannabis show minimal differences in craving. There were no significant group differences in blood-THC concentration post-cannabis use.

Conclusion: Results indicate that for some individuals who drink heavily, cannabis may serve as a substitute for alcohol, and craving reduction is a potential mechanism through which this could occur.